The present invention relates to sugar derivatives of indolopyrrolocarbazoles which exhibit topoisomerase I activity and are useful in inhibiting the proliferation of tumor cells.
Topoisomerases are vital nuclear enzymes which function to resolve topological dilemmas in DNA, such as overwinding, underwinding and catenation, which normally arise during replication, transcription and perhaps other DNA processes. These enzymes allow DNA to relax by forming enzyme-bridged strand breaks that act as transient gates or pivotal points for the passage of other DNA strands. Topoisomerase-targeting drugs appear to interfere with this breakage-reunion reaction of DNA topoisomerases. In the presence of topoisomerase active agents, an aborted reaction intermediate, termed a xe2x80x98cleavable complexxe2x80x99, accumulates and results in replication/transcription arrest, which ultimately leads to cell death.
The development of topoisomerase I active agents therefore offers a new approach to the multi-regimental arsenal of therapies currently used in the clinic for the treatment of cancer. An article in Cancer Chemother. Pharmacol [1994, 34 (suppl): S 41-S 45] discusses topoisomerase I active compounds that are in clinical studies and these have been found to be effective clinical anti-tumor agents. Structurally these clinical candidates are related to the alkaloid camptothecin.
Indolo[2,3-a]carbazole derivatives related to the Rebeccamycin class are disclosed (EP Appl. 0 545 195 B1 and 0,602,597 A2; Cancer Research 1993, 53, 490-494; ibid 1995, 55, 1310-1315) and claimed to exhibit anti-tumor activity; however the major mechanism of action of these derivatives may not be like camptothecin, which acts as a topoisomerase I poison.
Indolo[2,3-a]carbazole alkaloids such as rebeccamycin (U.S. Pat. Nos. 4,487,925 and 4,552,842) and its water-soluble, clinically-active analog, 6-(2-diethylaminoethyl)rebeccamycin (U.S. Pat. No. 4,785,085), are useful antitumor agents which target DNA. Furthermore, fluoroindolocarbazoles such as described in WO 98/07433 are antineoplastic agents with topoisomerase I inhibitory activity. Indolocarbazoles are also disclosed (WO 9530682) and claimed to exhibit anti-tumor activity. Hudkins, et al. have disclosed a series of fused pyrrolocarbazoles (WO 96/11933 and U.S. Pat. No. 5,475,110) and showed in vitro biological data such as inhibition of neuronal choline acetyltransferase (ChAT) and protein kinase C (PKC) inhibition for some compounds. U.S. Pat. No. 5,468,849 discloses certain fluororebeccamycin analogs as useful antitumor agents, along with a process for their production by fluorotryptophan analog feeding of a rebeccamycin-producing strain of Saccharothrix aerocolonigenes, preferably Saccharothrix aerocolonigenes C38,383-RK2 (ATCC 39243). Glicksman, et al. disclose indolocarbazole alkaloids (U.S. Pat. No. 5,468,872) which are different in structure from those of the present invention. Kojiri, et al. disclose indolopyrrolocarbazoles having a dissacharide substituent (WO 96/04293). Weinreb, et al. (Heterocycles 1984, 21, 309) and Kleinschroth, et al. (U.S. Pat. No. 5,043,335) have disclosed indolopyrrolocarbazole derivatives with a bridging furan moiety and McCombie, et al. (Bioorg. Med. Chem. Lett. 1993, 3, 1537) have reported a more functionalized bridged furan. Wood, et al. have reported the total synthesis of (+)xe2x88x92K252a (J. Am. Chem. Soc. 1995, 117, 10413), a related, naturally-occurring indolocarbazole alkaloid which has demonstrated PKC inhibitory activity. During the course of their total synthesis of (+)xe2x88x92K252a, Fukuyama, et al. (J. Am. Chem. Soc. 1999, 121, 6501) have also described the isolation of a cycloglycoside as an undesired product.
Danishefsky, et al., during the course of their first total synthesis of staurosporine (J. Am. Chem. Soc. 1996, 118, 2825), describe the synthesis of an intermediate N12, N13-bridged indolopyrrolocarbazole. Indolocarbazole derivatives with the nitrogens linked by a three-atom bridge have been reported to be potent PKC inhibitors (S. F. Vice, et al. Bioorg. Med. Chem. Lett. 1994, 4, 1333). The synthesis of simple indolocarbazole derivatives with C1xe2x80x2, C-5xe2x80x2-bridging or C1xe2x80x2, C3xe2x80x2-bridging glycosides have also been reported in the literature (B. M. Stolz, J. L. Wood Tetrahedron Lett. 1995, 36, 8543 and B. B. Shankar, S. W. McCombie Tetrahedron Lett. 1994, 35, 3005, respectively). Prudhomme, et al. disclose a series of antitumor indolocarbazoles derived from rebeccamycin which exhibit a carbohydrate attached to the two indole nitrogens, and reported their cytotoxicity and their topoisomerase I and PKC inhibitory activities to be in the millimolar to micromolar range (Bioorg. Med. Chem. 1998, 6, 1597). Despite these examples, there remains a need for novel and potent cytotoxic compounds useful for inhibiting topoisomerase I activity.
Thus according to a first embodiment of the first aspect of the present invention are provided compounds of Formula (I) and pharmaceutically acceptable salts and solvates thereof, useful for inhibiting topoisomerase I and the proliferation of tumor cells 
wherein
Z is selected from the group consisting of Formula (A), Formula (B), Formula (C), Formula (D), Formula (E), Formula (F) and Formula (G) 
R is hydrogen, OH, OC1-7alkyl, NH2, N(C1-3alkyl)2, or C1-7alkyl, wherein said C1-7alkyl or C1-3alkyl is optionally substituted with one or more substituents selected from the group consisting of halogen, CN, SR9, OR9 and NR9R10;
R1, R2, R3, R4 and R5 are each independently selected from the group consisting of hydrogen, C1-7alkyl, C3-7cycloalkyl, halogen, azido, NR9R10, NHC(O)NR9R10, NHC(O)OR9, C(O)OR9, SR9 and OR9, wherein said C1-7alkyl is optionally substituted with one or more substituents selected from the group consisting of halogen, CN, SR9, OR9 and NR9R10;
provided that no more than two of the variables selected from the group consisting of R1, R2, R3, R4 and R5 may be C3-7cycloalkyl, azido, NHC(O)NR9R10 or NHC(O)OR9;
R7 and R8 are independently OH or H or R7 and R8 together form xe2x95x90O;
R9 and R10 are independently selected from the group consisting of hydrogen, C1-7alkyl and C3-7cycloalkyl, wherein said C1-7alkyl is optionally substituted with one or more substituents selected from the group consisting of halogen, CN, OH, Oxe2x80x94C1-7alkyl, NH2 and N(C1-3alkyl)2; or
R9 and R10 together with the nitrogen atom to which they are attached form a non-aromatic 5-8 membered heterocycle containing one or two of the same or different heteroatoms selected from the group consisting of O, N and S;
m is 0 or 1; and
X1, X1xe2x80x2, X2 and X2xe2x80x2 are independently selected from the group consisting of hydrogen, halogen, cyano, OR9, xe2x80x94CF3, alkylcarbonyl, C-1-7alkyl, nitro, alkoxyaminoalkyl, NR9R10, SR9 and C(O)OR9; wherein said C1-7alkyl is optionally substituted with one or more substituents selected from the group consisting of halogen, CN, OR9, SR9 and NR9R10.
According to a first embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein Z is selected from the group consisting of Formula (A), Formula (C) and Formula (D).
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein Z is formula (A).
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein Z is formula (B).
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein Z is formula (C).
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein Z is formula (D).
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein m is 1.
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein m is 0.
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein R is hydrogen.
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein R7 and R8 together are xe2x95x90O.
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein R7 and R8 are each H.
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein X2xe2x80x2 and X2 are each F and X1 and X1xe2x80x2 are each H.
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein X2 is F and X2xe2x80x2, X1 and X1xe2x80x2 are each H.
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein X2xe2x80x2 is F and X2, X1 and X1xe2x80x2 are each H.
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein X2xe2x80x2, X2, X1 and X1xe2x80x2 are each F.
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein X2xe2x80x2 and X2 are each H and X1 and X1xe2x80x2 are each F.
According to another embodiment of the first aspect of the present invention are provided compounds of Formula (I) wherein R1, R2, R3, R4 and R5 are independently selected from the group consisting of H, F, OR9 wherein R9 is hydrogen or methyl.
Other embodiments of the first aspect of the present invention provide compounds of Formula (I) comprising two or more of the above embodiments of the first aspect suitably combined.
Embodiments of a second aspect of the present invention provide a method for inhibiting tumor growth in a mammalian host, particularly a human host, comprising the administration to said host of a tumor-growth inhibiting amount of a compound of the present invention, as defined herein.
Embodiments of a third aspect of the present invention provide a method for inhibiting tumor growth in a mammalian host comprising the administration to said host of a tumor-growth inhibiting amount of a pharmaceutical formulation of a compound of the present invention, as defined in the embodiments of the first aspect of the invention.
Other embodiments and aspects of the invention will be apparent according to the description provided below.
The description of the invention herein should be construed in congruity with the laws and principals of chemical bonding. An embodiment or aspect which depends from another embodiment or aspect, will describe only the variables having values and provisos that differ from the embodiment or aspect from which it depends. Thus, for example, an embodiment which reads xe2x80x9cthe compound of formula (I) according to the nth aspect of the invention, wherein R is NH2xe2x80x9d should be read to include all remaining variables with values defined in the nth aspect and should be read to further include all the provisos, unless otherwise indicated, pertaining to each and every variable in the nth aspect. Where a variable is defined as having a value of zero, it is understood that the bond attached to said variable should be removed. For example, if n=0 and Rxe2x80x94Xxe2x80x94Vn wherein n can be 0 or 1, then it is understood that the structure described is Rxe2x80x94X not Rxe2x80x94Xxe2x80x94. The numbers in the subscript after the symbol xe2x80x9cCxe2x80x9d define the number of carbon atoms a particular group can contain. For example xe2x80x9cC1-7alkylxe2x80x9d means a straight or branched saturated carbon chain having from one to seven carbon atoms including without limitation groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, t-butyl, n-pentyl, sec-pentyl, isopentyl, n-hexyl and n-heptyl. xe2x80x9cArylxe2x80x9d means an aromatic hydrocarbon having from six to ten carbon atoms; examples include phenyl and naphthyl. xe2x80x9cSubstituted arylxe2x80x9d or xe2x80x9csubstituted aralkylxe2x80x9d means an aryl or aralkyl group independently substituted with one to five (but particularly one to three) groups selected from the group consisting of C1-6alkanoyloxy, hydroxy, halogen, C1-6 alkyl, trifluoromethyl, C1-6alkoxy, C2-6alkenyl, C1-6alkanoyl, nitro, amino, cyano, azido, C1-6 alkylamino, and amido. The term xe2x80x9chalogenxe2x80x9d includes fluoro, chloro, bromo and iodo.
It is to be understood that the present invention includes any and all possible stereoisomers, geometric isomers, diastereoisomers, enantiomers and anomers, unless a particular description specifies otherwise.
The compounds of this invention can exist in the form of pharmaceutically acceptable salts. Such salts include addition salts with inorganic acids such as, for example, hydrochloric acid and sulfuric acid, and with organic acids such as, for example, acetic acid, citric acid, methanesulfonic acid, toluenesulfonic acid, tartaric acid and maleic acid. Further, in case the compounds of this invention contain an acidic group, the acidic group can exist in the form of an alkali metal salt such as, for example, a potassium salt and a sodium salt; an alkaline earth metal salts such as, for example, a magnesium salt and a calcium salt; and salts with organic bases, such as a triethylammonium salt and an arginine salt. The compounds of the present invention may be hydrated or non-hydrated.
The compounds of this invention can be administered in such oral dosage forms as tablets, capsules (each of which includes sustained release or timed release formulations), pills, powders, granules, elixirs, tinctures, suspensions, syrups and emulsions. The compounds of this invention may also be administered intravenously, intraperitoneally, subcutaneously, or intramuscularly, all using using dosage forms well known to those of ordinary skill in the pharmaceutical arts. The compounds can be administered alone but generally will be administered with a pharmaceutical carrier selected upon the basis of the chosen route of administration and standard pharmaceutical practice. Compounds of this invention can also be administered in intranasal form by topical use of suitable intranasal vehicles, or by transdermal routes, using transdermal skin patches. When compounds of this invention are administered transdermally the dosage will be continuous throughout the dosage regimen.
One aspect of the present invention involves administration of the compounds of the present invention, or pharmaceutically acceptable salts or solvates thereof, to a mammal implanted with a tumor or susceptible to cancer formation. In general the compound would be given in a dose range of from about 0.01 mg/kg to about the MTD (maximum tolerated dose). The dosage and dosage regimen and scheduling of a compound of the present invention must in each case be carefully adjusted, utilizing sound professional judgment and considering the age, weight and condition of the recipient, the route of administration and the nature or extent of the cancer disease condition. The term xe2x80x9csystemic administrationxe2x80x9d as used herein refers to oral sublingual, buccal, transnasal, transdermal, rectal, intramascular, intravenous, intraventricular, intrathecal, and subcutaneous routes. In accordance with good clinical practice, it is preferred to administer the instant compounds at a concentration level which will produce effective beneficial effects without causing any harmful or untoward side effects.
Procedures for the preparation of Formula (I) compounds are illustrated in Schemes 1-6 and the preparation of the key intermediates/starting materials is illustrated in Scheme 7. 
In Scheme 1, a selectively protected glycoside (1) was treated under Mitsunobu conditions (cf. O. Mitsunobu Synth., 1981, 1, 1), for example using triphenylphosphine and diisopropyl azodicarboxylate (DIAD), in a suitable solvent like benzene at room temperature to 100xc2x0 C., preferably at or around 80xc2x0 C., to give a 4xe2x80x2-bridged glycoside (2). Removal of the benzyl protecting groups could then be done using a conventional procedure involving hydrogenolysis over Pearlman""s catalyst (20% Pd(OH)2 on charcoal) to give a fully deprotected bridged glycoside (3). Alternatively, a partially deprotected glycoside could be prepared by treatment of the corresponding perbenzylated glycoside with iodine in acetic anhydride (cf. K. P. R. Kartha, R. A. Field Tetrahedron 1997, 53, 11753), followed by hydrolysis of the intermediate acetate. Subsequent treatment of this selectively deprotected glycoside with the well-known fluorinating agent DAST [(diethylamino)sulfur trifluoride], followed by debenzylation as before, then gives a monofluorinated bridged glycoside (4).
An alternative bridging procedure is shown in Scheme 2. Deprotection of the imide moiety of perbenzylated glycosides such as 5 was done by base-induced hydrolysis, followed by acidification to give an intermediate anhydride. The latter was conveniently converted to an imide using a suitable amine, such as that provided by reaction with a mixture of hexamethyldisilazane and methanol in dimethylformamide (cf. P. D Davis, R. A. Bit Tetrahedron Lett. 1990, 31, 5201). Selectively deprotected glycosides like 7 could then be prepared by treatment of the corresponding perbenzylated glycosides with iodine in acetic anhydride (cf. K. P. R. Kartha, R. A. Field Tetrahedron 1997, 53, 11753), followed by hydrolysis of the intermediate acetates. The resulting primary alcohol could then be activated, for example as its mesylate and subsequently the corresponding iodide, and induced to undergo elimination of the element of HI using a suitable amine base, such as 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), to give a vinyl ether 8. Treatment of this vinyl ether with iodine, in the presence of a suitable base such as potassium tert-butoxide, leads to a bridging reaction to give a 1xe2x80x2,5xe2x80x2-bridged glycoside 9. The resulting iodide (9) readily undergoes a radical-induced reduction, using for instance tri-n-butyltin hydride as the hydride source and 2,2xe2x80x2-azobisisobutyronitrile (AIBN) as a radical initiator, to give the corresponding 6xe2x80x2-deoxy bridged glycoside. Final removal of the benzyl protecting groups to give 10 could be effected using a number of standard methods, for example by treatment with boron tribromide. Alternatively, the iodide 9 could also be readily oxidized using a peracid, such as m-chloroperbenzoic acid, to give a 6xe2x80x2-hydroxy-substituted bridged glycoside (11). Final deprotection as before then gives derivative 12.
The aromatic core is also readily reduced as shown in Scheme 3. Following radical reduction of the iodide 13, the imide moiety is reduced by treatment with a reducing hydride, such as sodium borohydride, with further reduction using benzeneselenol to give a mixture of the corresponding lactams. Final deprotection as before then gives a mixture of the regioisomeric lactams 15 and 16.
In some instances, unprotected glycosides may conveniently be used to prepare bridged glycosides. For instance, as shown in Scheme 4, an unprotected glycoside (17) cyclizes under the previously mentioned Mitsunobu reaction conditions to give a 1xe2x80x2,6xe2x80x2-bridged glycoside (18). This strategy is advantageous in that it obviates the need for a final deprotection step.
Another useful approach to the synthesis 1xe2x80x2,6xe2x80x2-bridged glycosides is shown in Scheme 5. In this case, the previously mentioned glycoside (5) is mono-debenzylated as described before to give the 6xe2x80x2-deprotected glycoside 19. The latter undergoes a bridging reaction to give 20 under Mitsunobu conditions, for example by the use of a complex of trimethylphosphine and 1,1xe2x80x2-(azodicarbonyl)dipiperidine (ADDP) in a suitable solvent, such as benzene, at room temperature to around 100xc2x0 C., preferably at or about 80xc2x0 C. Removal of all of the benzyl protecting groups is then done as before to give the 1xe2x80x2,6xe2x80x2-bridged glycoside 21.
Mono-debenzylated glycosides may also be used to prepare selected bridged glycosides as shown in Scheme 6. Thus, the unprotected hydroxyl group of the tri-O-benzylglycoside 22 could be activated, for example as its mesylate, which may then undergo elimination of the element of methanesulfonic acid using a suitable amine base, such as diisopropylethylamine, to give a 1xe2x80x2,2xe2x80x2-bridged glycoside which is readily debenzylated as before to give 23.
A key intermediate sugar was prepared as shown in Scheme 7. Conversion of a commercially available methyl-xcex1-D-glucopyranoside (24) to a 4-deoxyglycoside (26) was done as reported by Barrette and Goodman (J. Org. Chem. 1984, 49, 176). Deprotection of the anomeric position could be done in two steps, first by treatment with benzenethiol and a Lewis acid, such as boron trifluoride etherate (cf. L. A. Paquette, J. A. Oplinger J. Org. Chem. 1988, 53, 2953), followed by hydrolysis of the resulting phenylthio sugar derivative (27) using N-bromosuccinimide in a suitable solvent, such as acetone or acetonitrile, in the presence of water (cf. B. Fraser-Reid, et al. J. Am. Chem. Soc. 1988, 110, 2662). Alternatively, deprotection of the anomeric position could be effected in one step by treatment with a suitable acid, such as 90% formic acid, to give the glucopyranoside (28) directly. Conversion of a glycopyranoside, such as 28, to a glycopyranosyl chloride (29) could be done according to a procedure reported by Iversen and Bundle (Carb. Res. 1982, 103, 29).
The compounds which constitute this invention and their methods of preparation will appear more fully from a consideration of the following examples which are given for the purpose of illustration only and are not to be construed as in any way limiting the scope of the invention.
Several intermediate compounds as well as other conventional starting materials, used in the preparation of final products of Formula I, were generally known in the literature or were commercially available. Representative syntheses of some of these compounds are nevertheless provided hereinbelow.
All anhydrous reactions were performed under an atmosphere of nitrogen or argon using either commercially available dry solvents or freshly distilled solvents. Melting points were determined in an open capillary tube with a Thomas-Hoover melting point apparatus and are uncorrected. Column chromatography was performed using EM Science silica gel 60 (230-400 mesh) with the designated solvent system as eluant. Thin-layer chromatography was done on E. Merck silica gel 60 F254 plates (0.5 mm). Hplc purity determinations were done using either a Shimadzu LC-10AS with a SPD-10AV UV-Vis detector and one of the following columns; YMC Combiscreen ODS-A (4.6xc3x9750 mm), or HP Zorbax SB-C18 (4.6xc3x97750 mm); or, an HP 1090 DR5 with a diode array detector and a Waters Nova-Pak C18 column (3.9xc3x97150 mm). Infrared spectra were recorded on a Nicolet Protxc3xa9gxc3xa9 460 FTIR as thin films or KBr pellets. 1HNMR spectra were recorded on either a Bruker AMX-400 or a Bruker ARX-500 NMR spectrometer and chemical shifts are expressed in parts per million (ppm or xcex4) with the solvent in use as internal standard. Coupling constants are given in hertz (Hz) and multiplets are designated as follows; singlet (s), doublet (d), triplet (t), quartet (q), muliplet (m), and broad (br). Low resolution mass spectra were determined on a Finnigan Matt TSQ-7000 triple stage quadrapole spectrometer (positive/negative ESI) operated in the negative ion mode.